The present invention relates to in-tank fuel modules having components made of plastic or polymeric materials. More specifically, it relates to in-tank fuel modules arranged to prevent the accumulation of and provide for the safe dissipation of electrostatic charges that might be generated as a result of fuel flow.
The in-tank fuel module for a fuel tank of a vehicle or other device employing an internal combustion engine typically includes a plurality of separate components, such as a reservoir, a fuel pump and motor, fuel filter and housing, a pressure regulator and housing, an aspiration jet pump and the like. It can happen that such components are made of non-conductive materials or may include elements that are electrically conductive; but, the electrically conductive element is electrically insulated from the associated electrical circuit that defines a ground plane. For instance, the conductive component may be disposed within a non-conductive plastic body.
Conductive, as well as non-conductive components of an in-tank fuel module are susceptible of accumulating an electrostatic charge. It is well known to employ an arrangement that provides for dissipation of such static charge to prevent excessive build-up. Various examples are described in U.S. Pat. Nos. 5,076,920; 5,647,330; 5,785,032; 6,047,685; 6,206,035 and 6,435,163.
As the investigation of electrostatic charge build-up in in-tank fuel modules proceeds, refinements in the overall scheme for protection evolve. The present invention results from this process. Not only does it recognize the advantage to be derived from implementing such protection in areas not previously considered significant, it also provides enhanced mechanisms for accomplishing an overall improvement in the protection afforded.
Specifically, an arrangement is provided to protect against build-up of electrostatic charge in areas not heretofore considered relevant to the solution of electrostatic discharge problem. One such area is the aspiration jet pump employed to aspirate fuel into the module reservoir. Another is the conductive arm of the fuel level sensing assembly. The invention further provides previously unknown mechanisms to provide charge dissipation capability.
To control build-up of the electrostatic charge in the components of an in-tank fuel module, it is known in the art to electrically connect the component to the vehicle ground plane, usually to the negative terminal of the battery that defines that electrical plane. It is known to use metal wires to electrically connect the components to the ground, or to other grounded conductive components that are connected to the vehicle ground plane. It is contemplated by this invention to provide new arrangements for providing such a ground path.
The fuel level sensor detects the fuel level in a fuel tank, usually through a float and pivotal arm physically located in or on the in-tank fuel module. An electric circuit having a variable resistance card is used. A movable cross bar or contact member coacts with the resister card to alter the circuit characteristics to change the reading on a fuel gauge. This circuit includes an electrical path that is extant within the module and is ultimately connected to the ground plane. It provides a previously unrecognized path for electrostatic charge dissipation.
Moreover, the fuel level sensor assembly usually includes a metallic float arm mounted on a non-conductive wiper retainer. The arm has a buoyant member at one end. The retainer is pivotally mounted on a base that is also non-conductive. Since the float arm is formed of a metallic material, the float arm is susceptible of collecting electrostatic charge. However, since the wiper retainer and the base are formed of a non-conductive plastic, any electrostatic charge collected in the metallic arm is unable to dissipate to the circuit ground plane. Connection of the metallic float arm to the conductor of the level sensor circuit resident in the module is a solution to both the problem of undesirable electrostatic accumulation and provision of an effective electrostatic charge dissipation path.